ipv6: Add neighbor helpers that use the ipv6 stub

Add ipv6 helpers to handle ndisc references via the stub. Update
bpf_ipv6_fib_lookup to use __ipv6_neigh_lookup_noref_stub instead of
the open code ___neigh_lookup_noref with the stub.
Signed-off-by: David Ahern <dsahern@gmail.com>
Reviewed-by: Ido Schimmel <idosch@mellanox.com>
Signed-off-by: David S. Miller <davem@davemloft.net>

include/net/ndisc.h

@@ -2,6 +2,8 @@
 #ifndef _NDISC_H
 #define _NDISC_H
 
+#include <net/ipv6_stubs.h>
+
 /*
  *	ICMP codes for neighbour discovery messages
  */
@@ -379,6 +381,14 @@ static inline struct neighbour *__ipv6_neigh_lookup_noref(struct net_device *dev
 	return ___neigh_lookup_noref(&nd_tbl, neigh_key_eq128, ndisc_hashfn, pkey, dev);
 }
 
+static inline
+struct neighbour *__ipv6_neigh_lookup_noref_stub(struct net_device *dev,
+						 const void *pkey)
+{
+	return ___neigh_lookup_noref(ipv6_stub->nd_tbl, neigh_key_eq128,
+				     ndisc_hashfn, pkey, dev);
+}
+
 static inline struct neighbour *__ipv6_neigh_lookup(struct net_device *dev, const void *pkey)
 {
 	struct neighbour *n;
@@ -409,6 +419,36 @@ static inline void __ipv6_confirm_neigh(struct net_device *dev,
 	rcu_read_unlock_bh();
 }
 
+static inline void __ipv6_confirm_neigh_stub(struct net_device *dev,
+					     const void *pkey)
+{
+	struct neighbour *n;
+
+	rcu_read_lock_bh();
+	n = __ipv6_neigh_lookup_noref_stub(dev, pkey);
+	if (n) {
+		unsigned long now = jiffies;
+
+		/* avoid dirtying neighbour */
+		if (n->confirmed != now)
+			n->confirmed = now;
+	}
+	rcu_read_unlock_bh();
+}
+
+/* uses ipv6_stub and is meant for use outside of IPv6 core */
+static inline struct neighbour *ip_neigh_gw6(struct net_device *dev,
+					     const void *addr)
+{
+	struct neighbour *neigh;
+
+	neigh = __ipv6_neigh_lookup_noref_stub(dev, addr);
+	if (unlikely(!neigh))
+		neigh = __neigh_create(ipv6_stub->nd_tbl, addr, dev, false);
+
+	return neigh;
+}
+
 int ndisc_init(void);
 int ndisc_late_init(void);
 

net/core/filter.c

@@ -4759,11 +4759,9 @@ static int bpf_ipv6_fib_lookup(struct net *net, struct bpf_fib_lookup *params,
 	params->rt_metric = f6i->fib6_metric;
 
 	/* xdp and cls_bpf programs are run in RCU-bh so rcu_read_lock_bh is
-	 * not needed here. Can not use __ipv6_neigh_lookup_noref here
-	 * because we need to get nd_tbl via the stub
+	 * not needed here.
 	 */
-	neigh = ___neigh_lookup_noref(ipv6_stub->nd_tbl, neigh_key_eq128,
-				      ndisc_hashfn, dst, dev);
+	neigh = __ipv6_neigh_lookup_noref_stub(dev, dst);
 	if (!neigh)
 		return BPF_FIB_LKUP_RET_NO_NEIGH;